A detailed experimental and numerical study on the ignition temperature of single micron-sized spherical iron particles

•The ignition frequency of spherical and non-spherical iron particle with diameters range from 17 to 45 μm at different ambient temperature and oxygen concentration were measured.•The experimental phenomena are highly consistent with the ignition theory (X.C. Mi, A. Fujinawa, J.M. Bergthorson, 2022).•It is estimated that iron particles with high specific surface area such as reduced iron powder or carbonyl iron powder have a significant lower ignition temperature. Measuring the ignition temperature of micron-sized iron particles can verify the ignition mechanism and aid in designing efficient iron powder combustion devices. This study captured the diameter, morphology and ignition status of iron particles with diameter range from 17 to 45 μm entering a stable high-temperature environment by high-speed cameras. The ignition frequency of iron particles at different ambient temperatures and oxygen concentration were recorded. Defining the ignition temperature as the ambient temperature at which the ignition frequency of iron particles exceeds 0.9, it was found that the ignition temperature of iron particles heated from room temperature and closer to a spherical shape is approximately 1140 K, while the non-spherical iron particles is around 1120 K. The ignition temperature is independent of particle diameter and ambient oxygen concentration. The theoretical method for estimating ignition temperature (X.C. Mi, A. Fujinawa, J.M. Bergthorson, 2022) aligns well with the experimental results. Theoretical analysis indicates that the oxidation mechanism at low temperatures (below 800 K) does not affect the ignition temperature, preheating does not effectively reduce the ignition temperature, and iron particles with high specific surface areas, such as sponge iron powder, exhibit significantly lower ignition temperatures. This study, for the first time integrates experimental investigation with theoretical models to systematically examine the ignition temperature of individual micron-sized iron particles under diverse conditions. The experimental approach allows precise in-situ characterization of particle diameter, particle morphology in different ambient oxygen concentration, providing insights into their respective effects on ignition temperature. Through comprehensive theoretical discussion and experimental validation, the ignition mechanism of iron particles is verified, offering crucial parameters for the design and optimization of efficient iron particle combus